Material Matters

Bill HarginThe first of a three-part series on designing around glass-weave skew.

Au: This column is a comprehensive follow-on to our June column. With some overlap, these may be read together or independently.

In June I discussed the differences between 1067 and 106 glass styles, introducing the concept of “glass-weave skew” or the “fiber-weave effect.” Here in part one of a series on glass-weave skew, I’ll introduce its causes and when or why a hardware designer might care. In part two, we will discuss mitigation techniques and cost, and in part three we’ll do a deeper dive on the impact of glass styles on precipitating or mitigating skew.

First, a memory. While writing this, I kept thinking of my first time on the German Autobahn, in the late 1990s. We were coming back from a HyperLynx SI workshop and – as weird as it sounds even 20 years later – my driver was going just under 240kph (~150mph). As the semi-naive American in the car, I thought I should offer some chitchat on the four-hour drive to Munich to keep the driver awake. In an almost robotic tone, my German counterpart said, “I cannot talk at this speed.” I don’t suppose I’ll ever forget that comment.

Read more: How to Avoid Getting Totally Skewed

And do you truly know the source of the material?

Read more: What’s the Difference between 106 and 1067 Glass?

Bill Hargin

The stack-up and materials are the backbone of a board design.

Read more: Material Selection for High-Speed PCB Design, Part 1

Bill HarginPart three of our series on Dk and Df characterization looks at stripline methods.

This is part three in a series that examines how the industry at-large characterizes laminates. It’s true such things are of little interest below 1GHz, but I suspect the relative comfort of the sub-GHz world has slipped into the distant past for many of us.

Part I summarized the “anarchy” that permeates this part of the PCB design world. Part II, last month’s column, pointed out a dozen different “standards” can be used to characterize Dk and Df. In fact, there’s little evidence to suggest the standardization process has led the industry to true standards. To me, “standard” means that if I measure something in Taipei, Tokyo, Toulouse or Toronto, I’m going to get pretty close to the same result if I follow a “standard” test method. That’s not what we have. Here in Part III, we’ll focus primarily on the electric-field (E-field) orientation of the measurement equipment.

Read more: Laminate Characterization Measurement Testing
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